Effect of Process Parameters on the Long-Run Print Consistency and Material Properties of Additively Printed Electronics

摘要

Traditionally, the printed circuit assemblies have been fabricated through a combination of imaging and plating based subtractive processes involving use of photo-exposure followed by baths for plating and etching to form the needed circuitry on rigid and flexible laminates. Additive electronics is finding applications for fabrication of IoT sensors. The emergence of a number of additive technologies poses an opportunity for the development of processes for manufacture of flexible substrates using mainstream additive processes, which are now commercially available. Aerosol-Jet printing has shown the capability for printing lines and spaces below 10 µm in width. The Aerosol-Jet system supports a wide variety of materials, including nanoparticle inks and screen-printing pastes, conductive polymers, insulators, adhesives, and even biological matter. The adoption of additive manufacturing for high-volume commercial fabrication requires an understanding of the print consistency, electrical and mechanical properties. Little literature exists that addresses the effect of varying sintering time and temperature on the shear strength and resistivity of the printed lines. In this study, the effect of process parameters on the resultant line-consistency, mechanical and electrical properties has been studied. Print process parameters studied include the sheath rate, mass flow rate, nozzle size, substrate temperature and chiller temperature. Properties include resistance and shear load to failure of the printed electrical line as a function of varying sintering time and varying sintering temperature. Aerosol-Jet machine has been used to print interconnects. Printed samples have been exposed to different sintering times and temperatures. The resistance and shear load to failure of the printed lines has been measured. The underlying physics of the resultant trend was then investigated using elemental analysis and SEM. The effect of line-consistency drift over prolonged runtimes has been measured for up to 10-hours of runtime. Printing process efficiency has been gauged a function of process capability index (Cpk) and process capability ratio (Cp). Printed samples were studied offline using optical Profilometry to analyze the consistency within the line width, line height, line resistance and shear load to study the variance in the electrical and mechanical properties over time.